The IDF is on heightened alert along the Lebanese border out of fear that Hizbollah will attack Israel while it is preoccupied with its war in the south.

The alert level was raised immediately after Israel began the operation in Gaza and increased after four Katyusha rockets hit the northern city of Nahariya last week, lightly injuring two people. On Sunday, gunshots were fired at an IDF patrol in the Golan Heights and three more rockets hit the north on Wednesday morning.

While Military Intelligence believes that small Palestinian terror groups in southern Lebanon were behind the attack on Nahariya, senior defence officials said Hizbollah was also involved.

“Nothing happens in southern Lebanon without Hizbollah knowing about,” one official said. “While Hizbollah may not have pulled the trigger, the organisation that did was likely working under its auspices.”

Beirut said it would investigate the breach of UN Resolution 1701, which ended the Second Lebanon War.

Israel, however, has been flying more intensely over Lebanon to monitor any activity indicating that Hizbollah plans to attack Israel, as it did in 2006 when it captured two IDF reservists while Israel was operating in Gaza following the capture of Gilad Shalit.

“We hope the northern border will remain quiet,” Defence Minister Ehud Barak said on Saturday evening. “But we are ready for any development.”

While the IDF believes that Hizbollah is not interested in a renewed conflict with Israel — particularly ahead of elections in Lebanon later this year — it is still seeking revenge for last February’s assassination in Damascus of the group’s military leader, Imad Mughniyah, which it attributes to Israel.

Israel also believes that Iran is urging Hizbollah to attack Israel in order to try and spare Hamas from devastation in the Gaza Strip.